Empirical investigation on buckling and post-buckling behaviour of cell liners

In nuclear-related facilities, many concete walls and slabs are lined with thin stainless steel plates in order to insure against the risk of accidental air leakage during a severe earthquake. These liners are forcibly deformed with the deformation of the concrete walls and slabs during an earthquake. The purpose of this paper is to obtain basic empirical data on the shearing behaviour of thin steel plates attached to concrete, especially to understand the relationship between the shear strain of the plate and its lateral displacement, as fundamental research on the safety of lining plates. A new apparatus for measuring the lateral displacement of a lining plate by continuously scanning its surface is tested. The apparatus proves to be quite effective for understanding the buckling wave of the lining plate and the essential behaviour of a thin steel plate attached to a concrete wall subject to a shear force is clarified.     

The method for surface functionalization of single-walled carbon nanotubes with fuming nitric acid

Surface functionalization of single-walled carbon nanotubes (SWCNTs) was carried out using fuming nitric acid as a NO₂ radical source. The surface double bonds of the SWCNTs reacted with the NO₂ radicals at 10–90 °C under sonication, and following treatment with aqueous NaOH yielded modified carbon nanotubes with high affinity for polar solvents such as dimethylformamide. The structure of the product was characterized using Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, and atomic force microscopy. FT-IR and XPS spectra revealed the product has OH groups (3400, 1200 cm⁻¹), which was expected due to the addition of NO₂ radicals to the surface double bonds and subsequent substitution with OH groups. C_1s curve fitting analysis of the XPS spectra was used to quantitatively determine the different functional groups on the surface, and the amount of COOH groups was found to be increased from 2.8% to 9.3% due to progressive oxidation by increasing the reaction temperature from 10 to 90 °C.     

Combined computational and experimental study of Ar beam induced defect formation in graphite

Irradiation of graphite, commonly used in nuclear power plants, is known to produce structural damage. Here, experimental and computational methods are used to study defect formation in graphite during Ar irradiation at incident energies of 50 eV. The experimental samples are analyzed with scanning tunneling microscopy to quantify the size distribution of the defects that form. The computational approach is classical molecular dynamic simulations that illustrate the mechanisms by which the defects are produced. The results indicate that defects in graphite grow in concentrated areas and are nucleated by the presence of existing defects.     

Dispersion tolerance and transmission distance of a 40-Gb/sdispersion management soliton transmission system

We investigate the tolerance of the variation of average dispersion in a 40-Gb/s dispersion-managed soliton (DMS) transmission system. It is theoretically shown that dispersion tolerance is governed by pulse broadening and soliton interaction, and that the largest dispersion tolerance can be achieved by optimizing the pulse energy depending on the transmission distance. We construct a 40-Gb/s recirculating loop transmission system and show that the dispersion tolerance of over 180 ps/nm, which is much larger than that of a linear nonreturn-to-zero (NRZ) format system, can be realized by the optimization of the pulse energy at a transmission distance of more than 1000 km     

Removal of fluoride ions from water by adsorption onto carbonaceous materials produced from coffee grounds

Carbonaceous material for the removal of fluoride ions from water was prepared from coffee grounds (CGs) by calcination and subsequent HCl treatment. The characteristics of the CGs, including the surface area, mean pore diameter, pore volume, and surface functional groups were determined, and the morphological characteristics were evaluated using scanning electron microscopy. The adsorption isotherms, saturated amount of fluoride ions adsorbed, and the effect of contact time and temperature on the adsorption of fluoride ions were investigated for a sample of tap water. The specific surface area of CG calcined at 600° (CG600) was larger than that of CGs calcined at 400, 800, and 1000°. Phenolic, lactonic, and carboxyl groups were detected on the CG600 surface. The adsorption capacity of the carbonized CGs for fluoride was ranked in the order CG400 < CG1000 < CG800 < CG600 (where the numeral indicates the carbonization temperature), whereas virgin CG and CG600-NAT (not treated with hydrochloric acid solution) did not exhibit any adsorption ability for fluoride ions. The amount of fluoride ions adsorbed onto CG600 increased with increasing temperature and was consistent with chemical adsorption. The mechanism of adsorption of fluoride ions onto CG600 proceeded via ion exchange with chloride ions (1:1) present on the surface of CG600. The adsorption isotherms were fitted to the Freundlich and Langmuir equations. Moreover, CG600 showed an acceptable adsorption capacity for fluoride ions present in tap water.     

A proposed method of predicting ship collision damage

In the past, research on ship collision strength has centered on nuclear ship structures, but now emphasis is shifting to low-energy collisions of ordinary ships carrying hazardous cargoes including crude oil.A ship collision is too complex to study using theoretical methods alone, yet tests with small-scale models of thin steel plate fail to duplicate actual ship collision damage for the following reasons:

1. (1) The fracture of actual ship shell plate and model shell plate defies the law of similarity;

2. (2) Some structural members are usually omitted for ease of fabrication in relatively small models.

Accordingly, the authors propose a method for predicting ship collision damage that resorts to three combined experiments:

1. (1) A fundamental test determining the initiation of plate fracture;

2. (2) A local structure model test evaluating the effects of structural details;

3. (3) A structural model test investigating the deformation of a ship hull.

This paper reviews, by way of example, some results of the experimental studies which the authors have performed.The laws of similarity proved very important in the study of plate fracture.The authors believe that the proposed method will prove useful especially in dealing with low-energy ship collisions.     

New consideration on flutter properties based on step-by-step analysis

This paper studies the coupled flutter mechanism of plate and long span bridges based on step-by-step analysis (SBS). Fundamental flutter modes are defined based on amplitude ratio and phase difference between heaving and torsional motions. Furthermore, a formula remarkably similar to the Selberg formula can be derived by use of the particular simplified flutter-onset condition. In the process of SBS analysis, some torsional divergent velocities where the torsional rigidity becomes zero can be defined. Finally, the flutter-behavior of an elastic model of the complete Akashi-Kaikyo Bridge, which is the longest suspension bridge in the world, is studied from the point of view of flutter in 2 degrees of freedom, namely heaving and torsional motion, taking into account the structural coupling effect of additional torsional displacement induced by horizontal displacement as a structural coupling property.